Little Jerry of the Monotones in "Proud."
I first saw their song "Telephone Rock" on the Rock 'N Roll VHS and instantly fell in love with them as a Muppet band. Seeing them cameo in Grover's exit lecture and the Monotones singing back-up for Don Music in "Mary Had a Bycicle" surprised me. Seeing more of their songs surface on YouTube years later made me appreciate them even more.